Last month, former Colorado radio personality Robert “Jackson” Mueller declared he had bad blood with a certain international pop superstar.

Mueller said he showed up at a meet-and-greet for Taylor Swift after a Denver show in 2013 with his girlfriend. He said that, during a last-minute photo op, Swift put her arm around his shoulder. The camera flashed, and that appeared to be that.

Just another day in the radio biz.

However, after the picture was taken, Mueller said one of Swift's security team accused him of inappropriately touching the singer.

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And, in a lawsuit against Swift filed in September, Mueller said he lost his $150,000 job on the “Ryno and Jackson” show two days after the meet-and-greet because of that false accusation.

"Mueller steadfastly maintains that no inappropriate contact of any kind occurred between him and Ms. Swift,” he said in his lawsuit.

Now, Swift has replied to Mueller's lawsuit – and she isn't happy. In documents filed in U.S. District Court in Colorado, Swift not only denied Mueller's charges, but countersued, alleging assault.

“In the course of his meet and greet with Ms. Swift, Mueller intentionally reached under her skirt, and groped with his hand an intimate part of her body in an inappropriate manner, against her will, and without her permission,” Swift's lawsuit reads. “Mueller did not merely brush his hand against Ms. Swift while posing for the photograph; he lifted her skirt and groped her.”

When Mueller “groped her bottom,” the singer, “was surprised, upset, offended, and alarmed” – then had to go play a show for 13,000 people.

“She has held thousands of meet-and-greet events for both fans and radio station personnel,” the lawsuit reads. “In those thousands of events, she has been inappropriately groped one time – by Mueller.”

The lawsuit also made clear the physical differences between Swift and the radio personality.

“Mueller is approximately 6'3 tall and weighed over 200 pounds at the time he inappropriately put his open hand on Ms. Swift's bottom and groped it,” the lawsuit reads. “He was much larger than Ms. Swift” – who is often said to be 5-foot-10.

The singer rejected Mueller's contention, in his lawsuit, that another staff member of his radio station was the one who transgressed.

“Mueller's newfound claim that he is the ‘wrong guy’ and, therefore, his termination from KYGO was unjustified, is specious," Swift's suit read. "Ms. Swift knows exactly who committed the assault – it was Mueller.”

The lawsuit also claimed Mueller “was twice terminated from on-air radio positions he held with other radio stations” and, before his six-month stint at KYGO, had not been on the air since 2006.

"The radio station was given evidence immediately after the incident," Swift spokesman Tree Paine said last month. “They made their independent decision.”

Swift's suit it “will serve as an example to other women who may resist publicly reliving similar outrageous and humiliating acts.” Any damages “will be donated to charitable organizations dedicated to protecting women from similar acts of sexual assault and personal disregard.”